Streptococcus mutans produces several components that bind to basement membranes and endothelial cells of kidney in vitro. These adhesins are secreted into the environment during growth and are also associated with the bacterial cell surface. It is believed that these substances may leach naturally into blood vessels of the oral cavity, or enter as a consequence of trauma to oral tissues or by parenteral immunization. In rabbits, the interaction of S. mutans components with kidney results in a severe nephritis that shows many histological, immunopathological, and serological features of streptococcus- associated nephritides in man. Pathogenesis may result from either direct toxicity of the tissue-bound adhesin or in situ activation of the complement cascade by the regular or alternative pathways. The long range goals of this project are to: a) understand the mechanisms of adhesin binding and pathogenesis; b) to improve the safety of prospective carries vaccines by assuring exclusion of these hazardous factors; c) devise prophylactic or therapeutic measures for streptococcus- associated nephritis. Specifically, the nature of the interactions between known S. mutans adhesions (LTA and proteins P57, P48, P40 and P30) and kidney components in vitro will be defined. The kidney-binding pattern of each purified adhesin will be characterized by immunofluorescence and immunoenzyme stains in light microscopy. Binding specificities of radiolabeled adhesins and the identities of the corresponding kidney components will be determined using isotopic dilution techniques and competitive inhibition assays using purified tissue components; e.g., laminin and heparan sulfate. Photoactivated crosslinking reagents will be used to covalently couple streptococcal protein to its kidney receptor which will then be isolated and characterized. The in vivo binding activities and pathogenic properties of purified S. mutans adhesins will be studied in a rabbit experimental model. The effects of infusion and perfusion of kidneys and intravenous injections of rabbits will be evaluated by microscopic analyses or renal biopsies using immunofluorescence, immunoenzyme and histological stains. Electron microscopy with immunogold labelling will also be used. In vivo experiments will also reveal the modulating effects of antibodies, complement and other serum components on adhesin binding. Finally, bacteria in dental plaque will be tested for both cell wall-associated and extracellular adhesins using immunofluorescence and electron microscopy.